Mapping rectifier of earth{40 s surface radiation signals scanned by artificial satellite

ABSTRACT

Disclosed is a device to obtain, through a special cathode-ray tube an optical system, a radiation image polarstereographically mapped directly from radiation scanning signals received from an artificial satellite.

I Umted States Patent 1 in] 3,718,756

Watanabe [451 Feb. 27, 1973 MAPPING RECTIFIER OF EARTH 'S f r nc CitedSURFACE RADIATION SIGNAL UNITED STATES PATENTS 3,026,765 3/1962Guarricini [75] Inventor: Kantaro Watanabe, Tokyo, Japan 3,319,1055/1967 Koda 3,401,595 9/1968 Dinhobel ..355/52 [73] Assigneez ResearchCorporation, New York,

Primary Examiner-H0ward W. Britton 22 F1 M 14 71 Attorney-Robert S.Dunham, P. E. Henninger, Lester 1 w. Clark, Gerald w. Griffin, Thomas F.Moran, PP 143,453 Howard J. Churchill, R. Bradlee Boal, Christopher C.Dunham, Robert Scobey, Henry T. Burke and Ivan S. 52 u.s.c|. ..l78/6.7R, l78/6.8, 343/17,

355/52 57 ABSTRACT [51] Int. Cl ..G0ls 7/06, G03b 27/68, H04n 1/24 58Field of Search ..178/6.5, 6.7 R, 6.8; 343/5, Disclosed is a device toobtain, through a special cathode-ray tube an optical system, aradiation image polarstereographically mapped directly from radiationscanning signals received from an artificial satellite.

7 Claims, 2 Drawing Figures PATENTED FEB 2 71975 INVENTOR MAW/4R0MRI/VASE BY 0'! I. fZil/rqkbu earths surface,

MAPPING RECTIFIER F EARTH '8 SURFACE RADIATION SIGNAL SCANNED BYARTIFICIAL SATELLITE BACKGROUND OF THE INVENTION Some artificialsatellites, as for example the meteorological satellite Nimbus, scanwith a radiometer the earths surface (at ground, sea and cloud levels)nearly perpendicularly to the satellite orbital plane to measure theintensities of the radiation emitted by the earths surface, the solarradiation reflected by the etc., and transmit the radiation scanningsignals in sequence to a ground station by radio. The series ofradiation scanning signals received by the ground station are reproducedin the form of a radiation image on a sheet of photographic film orfacsimile photosensitive paper.

Because the earths surface is spherical, the radiation image thusobtained is more distorted in a portion corresponding to a greaterscanning angle with respect to the vertical axis, in other words, in anarea closer to the horizon. It is therefore necessary to rectify suchdistortion in the radiation image and then to convert the rectifiedimage into the form of a polarstereographic, Lambert or Mercator mapwhen the radiation image transmitted from an artificial satellite is tobe used for scientific purposes. It is also necessary to take into account the orbital motion of the satellite and the rotation of the earthwith respect to the satellite orbital plane SUMMARY OF THE INVENTION Theinvention relates to providing mapping rectification of earths surfaceradiation scanned by an artificial satellite along scan lines which aresubstantially perpendicular to the satellite orbital plane. Thesatellite transmits radiation scan signals which vary as a function ofradiation parameters of each scan line. These radiation scan signalstransmitted by the satellite are applied to a specially designed cathoderay tube which has a concave screen congruent with a spherical surfaceto generate on the screen a succession of images, each imagecorresponding to a scan line and having a visible parameter, such aslight intensity, varying as the radiation parameter of the scan line towhich it corresponds. A camera is placed in the vicinity of thespherical surface such that the camera lens front nodal point is on thespherical surface at a point which corresponds either to the North orSouth Pole of the earth. The front nodal point of the camera and theimage which is shown in the cathode ray tube screen are positioned withrespect to the spherical surface to reflect the position, with respectto the earth North Pole, of the satellite scan line which generates theimage on the cathode ray tube.

The factors for which compensation must be made are the fact that thescan lines are along a spherical surface, the fact that the satelliteorbits the earth, and the fact that the earth rotates with respect tothe satellite orbital plane. The compensation for the spherical surfaceof the earth is made by means of the concave surface of the cathode raytube screen. A compensation for the orbital motion of the satellitearound the earth is made by means of moving the cathode ray tube screenand the camera with respect to each other along the spherical surface. Acompensation for the earths rotation is made by means of rotating thecamera (and the film in it) around an axis passing through the frontnodal point of the camera lens and through the center of the sphericalsurface. As a result, the image on the film inside the camera, which isperpendicular to the axis of rotation of the camera, is apolarstereographic map projection of the satellite scan lines.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a diagram illustrating theprinciple of radiation scanning related to a device according to thepresent invention.

FIG. 2 is a diagram briefly illustrating an embodiment of the invention.

DETAILED DESCRIPTION The circle in FIG. 1 represents the earth (or asphere similar to the earth) as viewed from an infinitely distant pointin the plane of the equator. N denotes the North pole and S denotes theSouth pole. Arc ABM represents a scanning line on the earths surface inthe part scanned by a radiometer on an artificial satellite when theartificial satellite is orbiting right above point M. If the radiationimage on the scanning line is reproduced on a spherical surface similarto the earths while a relationship similar to the actual scanning ismaintained, and the reproduced image is photographed on a photosensitiveplane (for example, photographic film) placed perpendicularly to theearth s axis NS, by a camera having the front nodal point of its lensset at the point corresponding to South Pole S when radiation scanningis effected on the northern hemisphere, or at the point corresponding toNorth Pole N when radiation scanning is effected on the southernhemisphere, the photographed image AMB will be similar to the imageA"M"B formed by projecting the earths surface scanning line ABM from theSouth Pole S (or from the North Pole N) on the tangential plane at theNorth Pole N (or the South Pole S). Therefore, image A'M'B' onphotosensitive plane F precisely coincides with a polarstereographicmap.

The position of the radiation scanning line on the earths surfacescanned by a radiometer shifts from time to time as the artificialsatellite orbits. A radiation image of the earths surface, as rectifiedinto a polarstereographic map, can be obtained from a series ofradiation scanning signals transmitted from the artificial satellite byphotographing the radiation scanning line images, reproduced on theaforementioned sphere, on one photosensitive plane with the camera atpoint S (or point N) while the image position is shifted from time totime so as to maintain a relationship similar to the actual radiationscanning of the earths surface.

Although it is assumed in the foregoing description that the artificialsatellite orbits around the earth which is not rotating but stationary,subpoint M, right below the artificial satellite, of the scanning lineon the earth s surface gradually shifts westward, from the pointinvolved in the above description, on the map because the earth rotates.To obtain an accurate map image by compensating for the earth rotation,it is necessary that the camera at point S (or point N) be rotatedaround the earths axis NS at a certain constant angular velocitydetermined by the nodal period of the artificial satellite and theangular velocity of the earth rotation.

FIG. 2 briefly illustrates a mapping rectifier to realize theabove-mentioned principle. Antenna 1 receives the radiation scanningsignals transmitted from an artificial satellite. Receiver circuit 2reproduces on cathode-ray tube 3 the images of the signals received. Thesurface of the cathode-ray tube screen is concave so as to form asegment of a spherical surface represented by broken line 4. Thescanning line image produced on the cathode-ray tube screen is made tobe similar to the radiation scanning line on the earths surface scannedby a radiometer, by means of the electron-beam deflecting circuit of thecathode-ray tube. Center point M on the image corresponds to thesubpoint right below the artificial satellite at the time the radiometeron the artificial satellite scans the subpoint. With photographic lenswhose front nodal point is set at point S (or point N) which issymmetric, with respect to the center of the sphere, to the point N (orpoint S) on the spherical surface corresponding to the position of theNorth Pole (or South Pole) of the earth at the time of theabove-mentioned scanning, an image coinciding with a polarstereographicmap can be obtained, as mentioned previously, by photographing the imageshown on the cathode-ray tube screen on a photosensitive plane 6 whichis placed perpendicularly to the axis NS.

When the succeeding scanning signal image is shown on the cathode-raytube, the cathode-ray tube screen is slid along spherical surface 4 in arelation, with respect to spherical surface 4, to the actual orbitingcondition of the artificial satellite, and simultaneously thephotographic lens 5 and the photosensitive plane 6 are rotated aroundaxis NS at an angular velocity determined by the nodal period of theartificial satellite and the angular velocity of the earth rotation, tophotograph the image on the same photosensitive plane 6. By successivelyphotographing images in the same manner, a radiation image of the earthssurface, as polarstereographically mapped, can be obtained from a seriesof radiation scanning signals transmitted from the artificial satellite.

In place of sliding the cathode-ray tube screen along spherical surface4, the camera lens 5 and the photosensitive plane 6 may be slid alongthe spherical surface 4 while the cathode-ray tube 3 is fixed.

I claim:

1. Providing mapping rectification of earths surface radiation scannedby an artificial satellite along scan lines which are substantiallyperpendicular to the satellite orbital plane, said satellitetransmitting radiation scan signals varying as a function of a radiationparameter along each scan line, comprising the steps of: applying theradiation scan signals transmitted by the satellite to a cathode raytube having a concave screen congruent with a spherical surface togenerate on the screen a succession of images, each image correspondingto a scan line and having a visible parameter which varies as theradiation parameter of the scan line to which it corresponds; placingthe front nodal point of a photographic camera at a point on saidspherical surface which corresponds to one of the North and South polesof the earth and which is at the same relationship with the image on thecathode ray tube screen with respect to the spherical surface as therelationship between the scan line and the earth pole corresponding tothe pole at which the camera lens front nodal point is placed;photographing the image on a photosensitive surface contained by thecamera, said photosensitive surface placed perpendicularly to a lineconnecting the camera lens front nodal point and the center of saidspherical surface.

2. Providing mapping rectification as in claim 1 including providing acompensation for the earths rotation with respect to the satelliteorbital plane by means of rotating the photosensitive surface inside thecamera around an axis connecting the front nodal point of the cameralens and the center of the spherical surface at a velocity correspondingto the earths rotation with respect to the satellite orbital plane.

3. Providing mapping rectification as in claim 1 including providingcompensation for the satellite orbital motion by establishing andmaintaining relative motion between the cathode ray tube and the camera,with the front nodal point of the camera remaining on the sphericalsurface and the cathode ray tube screen remaining congruent with thespherical surface, said relative motion corresponding to the relativedisplacement of satellite scan lines with respect to the earth poles.

4. Providing mapping rectification as in claim 3 including providingcompensation for the earths rotation with respect to the satelliteorbital plane by means of rotating the photosensitive surface in thecamera around an axis connecting the front nodal point of the cameralens and the center of the spherical surface at a constant velocitycorresponding to the rotation of the earth with respect to the satelliteorbital plane.

5. Providing mapping rectification of earth's surface radiation scannedby artificial satellite along scanning lines comprising the steps ofreceiving from an artificial satellite radiation scanning signals of theearths surface, applying said signals to a cathode-ray tube having aspherically concave screen surface to generate an image on said concavescreen surface, the attitude and shape of said image being madeproportional in attitude and shape to the actual attitude and shape ofthe radiation scanning lines on the earths surface by appropriatelydeflecting the electron beam of said cathode-ray tube.

6. Providing mapping rectification of earths surface radiation scannedby artificial satellite according to claim 5 including placing the frontnodal point of a camera lens at a point corresponding to one of theSouth and North Poles of the earth on a spherical surface whichcoincides with the screen surface of the above-mentioned cathode-raytube, and causing an image produced on said cathode-ray tube screen tocoincide with a polarstereographic map by projecting said image on aphotosensitive plane that is placed perpendicularly to a straight lineconnecting the center of said spherical surface and the front nodalpoint of said lens.

7. Providing mapping rectification of earth's surface radiation scannedby artificial satellite according to claim 6, wherein an accurateradiation image of the earth's surface is obtained aspolarstereographically mapped by compensating for the effect of theearth rotation by means of photographing the image shown on thecathode-ray tube screen while rotating the camera, with the front nodalpoint of the camera lens being placed at a point corresponding to one ofthe South and North Poles of the earth on the spherical surface thatcoincides with the screen surface of said cathode-ray tube around anaxis passing through said one of the South and North poles and throughthe center of said spherical surface.

* t a: a: 5

1. Providing mapping rectification of earth''s surface radiation scannedby an artificial satellite along scan lines which are substantiallyperpendicular to the satellite orbital plane, said satellitetransmitting radiation scan signals varying as a function of a radiationparameter along each scan line, comprising the steps of: applying theradiation scan signals transmitted by the satellite to a cathode raytube having a concave screen congruent with a spherical surface togenerate on the screen a succession of images, each image correspondingto a scan line and having a visible parameter which varies as theradiation parameter of the scan line to which it corresponds; placingthe front nodal point of a photographic camera at a point on saidspherical surface which corresponds to one of the North and South polesof the earth and which is at the same relationship with the image on thecathode ray tube screen with respect to the spherical surface as therelationship between the scan line and the earth pole corresponding tothe pole at which the camera lens front nodal point is placed;photographing the image on a photosensitive surface contained by thecamera, said photosensitive surface placed perpendicularly to a lineconnecting the camera lens front nodal point and the center of saidspherical surface.
 2. Providing mapping rectification as in claim 1including providing a compensation for the earth''s rotation withrespect to the satellite orbital plane by means of rotating thephotosensitive surface inside the camera around an axis connecting thefront nodal point of the camera lens and the center of the sphericalsurface at a velocity corresponding to the earth''s rotation withrespect to the satellite orbital plane.
 3. Providing mappingrectification as in claim 1 including providing compensation for thesatellite orbital motion by establishing and maintaining relative motionbetween the cathode ray tube and the camera, with the front nodal poiNtof the camera remaining on the spherical surface and the cathode raytube screen remaining congruent with the spherical surface, saidrelative motion corresponding to the relative displacement of satellitescan lines with respect to the earth poles.
 4. Providing mappingrectification as in claim 3 including providing compensation for theearth''s rotation with respect to the satellite orbital plane by meansof rotating the photosensitive surface in the camera around an axisconnecting the front nodal point of the camera lens and the center ofthe spherical surface at a constant velocity corresponding to therotation of the earth with respect to the satellite orbital plane. 5.Providing mapping rectification of earth''s surface radiation scanned byartificial satellite along scanning lines comprising the steps ofreceiving from an artificial satellite radiation scanning signals of theearth''s surface, applying said signals to a cathode-ray tube having aspherically concave screen surface to generate an image on said concavescreen surface, the attitude and shape of said image being madeproportional in attitude and shape to the actual attitude and shape ofthe radiation scanning lines on the earth''s surface by appropriatelydeflecting the electron beam of said cathode-ray tube.
 6. Providingmapping rectification of earth''s surface radiation scanned byartificial satellite according to claim 5 including placing the frontnodal point of a camera lens at a point corresponding to one of theSouth and North Poles of the earth on a spherical surface whichcoincides with the screen surface of the above-mentioned cathode-raytube, and causing an image produced on said cathode-ray tube screen tocoincide with a polarstereographic map by projecting said image on aphotosensitive plane that is placed perpendicularly to a straight lineconnecting the center of said spherical surface and the front nodalpoint of said lens.
 7. Providing mapping rectification of earth''ssurface radiation scanned by artificial satellite according to claim 6,wherein an accurate radiation image of the earth''s surface is obtainedas polarstereographically mapped by compensating for the effect of theearth rotation by means of photographing the image shown on thecathode-ray tube screen while rotating the camera, with the front nodalpoint of the camera lens being placed at a point corresponding to one ofthe South and North Poles of the earth on the spherical surface thatcoincides with the screen surface of said cathode-ray tube around anaxis passing through said one of the South and North poles and throughthe center of said spherical surface.